Automatic mechanical transmission systems comprising mechanical transmissions and controls and actuators to automatically shift same, usually electronically controlled in accordance with sensed inputs and predetermined logic rules, are known. Examples of such systems may be seen by reference to U.S. Pat. No. 4,648,290, U.S. Pat. No. 4,642,771, U.S. Pat. No. 4,595,986, U.S. Pat. No. 4,527,447, U.S. Pat. No. 4,361,060, U.S. Pat. No. 4,140,031 and U.S. Pat. No. 4,081,065, the disclosures of which are hereby incorporated by reference. Such systems may also be seen by reference to SAE Paper No. 831776 titled "AUTOMATED MECHANICAL TRANSMISSION CONTROLS," the disclosure of which is hereby incorporated by reference. Fault tolerance logic routines for automatic transmissions are known as may be seen by reference to U.S. Pat. No. 4,922,425, U.S. Pat. No. 4,849,899 and U.S. Pat. No. 4,899,279, the disclosures of which are hereby incorporated by reference.
Electronic and other engine fuel control systems wherein the fuel supplied to the engine may be modulated to provide a desired engine speed, regardless of the operator's setting of the throttle pedal, are known in the prior art. Such systems may be seen by reference to U.S. Pat. No. 4,081,065, U.S. Pat. No. 4,361,060, U.S. Pat. No. 4,792,901 and by reference to SAE J1922 and SAE J1936 electronic engine control standards, and related standards SAE J1708, J1587 and J1843, all of which are hereby incorporated by reference.
With automated transmission systems, particularly those derived from a manual nonsynchronized mechanical transmission, the conditions of tooth butting and/or tooth buzzing may occur, for instance when the vehicle starts from a stop. Tooth butting occurs when the ends of the teeth of the jaw clutch members come into abutment rather than axial interengagement, for instance when the rotational speeds of a sliding clutch and of a gear are equal or nearly equal when a gear engagement is initiated. Eventually the speeds of the two jaw clutch members will change and slip occurs causing a gear buzz (chatter) during the ensuing engagement. Tooth buzzing thus occurs when the ends of the butted jaw clutch teeth go into a grinding relative rotation rather than into axial interengagement as one of the clutch members is rotated to overcome butting. In such transmission systems, especially if the master friction clutch or torque disconnect clutch is not closely modulated, it is desirable to provide logic routines for detecting and for overcoming such tooth butt or tooth buzz conditions.
Furthermore, during a shift sequence of the gears of a transmission, it is possible to not fully engage the sliding clutch due to torque lock. Torque lock occurs when, due to torque being transmitted, a higher frictional force exists than the input force trying to slide the clutch into full engagement. During torque lock, a sudden torque decrease or reversal may allow the gear to fully engage, but until that occurs all of the power flow for the gear is through the partial engagement. Under normal torque lock conditions, the sliding clutch will not engage further until a torque reversal has occurred. The same phenomenon occurs during a gear butt condition.
A conventional method of recovery from tooth butting and tooth buzzing has been to continue pushing the clutch collar and gear toward engagement, or to recycle the gear box back to neutral and reinitiate engagement multiple times until complete, as disclosed by U.S. Pat. No. 5,099,711, assigned to the assignee of the present invention and hereby incorporated by reference.